When broadcasting TV programs involving TV viewers and requesting responses from TV viewers by telephone, facsimile or the like, such as quiz programs, debating programs, telephone order programs, ticket booking programs, questionnaire programs and fund-raising campaign programs, the broadcasting side often superimposes information for the TV viewers, such as the reception phone number and the account number of the remittee over pictures displayed on the screen for a certain period of time or explains the information by speeches. However, since the information is broadcast in pictures or speeches for a fixed period of time, the TV viewers need to write the information down to keep the information, such as the phone number and such.
If the TV receiver has a picture-in-picture function and a still subscreen function, i.e., a function to display a picture in a subscreen, the information, such as the phone number, can be continuously displayed in a still picture on the still subscreen when the TV viewer selects the still subscreen function. However, the TV viewers must keep writing materials and a memo pad at hand and, even if writing materials and a memo pad are available, it is troublesome to make a note of the information, the unfamiliar phone number and the like may possibly be written down mistakenly or the notes may be lost. Furthermore, even if the TV receiver has a picture-in-picture function, the TV viewers often fail to set the TV receiver in a picture-in-picture mode in time due to delayed picture-in-picture mode setting operation and miss displaying the information.
Incidentally, an experimental two-way broadcasting service commonly referred to as EDS, or Extended Data Service, is being conducted in North America broadcasts, in most cases, information necessary for responding to a broadcast program by a character multiplex broadcasting system, in which information is broadcast in a multiplex mode in the vacant horizontal blanking intervals of vertical blanking intervals, because the information has a large quantity of data including bit map data. However, the TV receiver needs a character multiplexing tuner having a complicated circuit configuration including a waveform equalizer and a data slicer to select character information from broadcast TV signals and to decode the same. Accordingly, the TV receiver equipped with such a character multiplex tuner is necessarily expensive and must be inevitably equipped with different circuits, for example, for the NTSC broadcasting system, the BS broad casting system, the CS broadcasting system and the MUSE broadcasting system.
On the other hand, a TV receiver for receiving information, which is necessary for responding to broadcast programs, broadcast in a two-way broadcasting mode by a character multiplex broadcasting system used in Japan, the TV receiver must be equipped with a character multiplex broadcast tuner provided with a large amount of Japanese font data to meet the Broadcast Law. Therefore, TV receivers for domestic use are generally more expensive than those for export to Western countries where the Japanese font data is typically not needed. Although Direct TV data broadcasting service using one of the channels of satellite broadcasting system is in an experimental stage in Japan, this data channel can be used only by TV receivers equipped with a BS tuner.